1. Field of the Invention
The present invention relates to the field of database management. Particularly, the present invention relates to a method and to an information technology infrastructure for establishing a log point for automatic recovery of federated databases to a prior point in time.
2. Description of the Related Art
A failure, e.g. a media failure in a computer or in a database system often requires a recovery to currency in order to rescue important data. Individual recovery of each affected component can bring the entire system to a consistent state. However, this procedure cannot be used if the system needs to be recovered to any point in time in the past. Namely, there is no common database log for all the participating components of the system.
It is possible to stop/quiesce and update processing for all the components of the system, register that time or the associated recovery log point and use it as a target in subsequent recovery. The recovery target point established in this way is indeed a point at which the intra- and inter-component consistency is guaranteed, but the process of obtaining these points is prohibitively disruptive for normal functioning of the system, complex and error prone in terms of human interaction, and poses a major hurdle in achieving a high level of continuous operations which is an important requirement of the business critical applications.
A conventional method and a system is known for establishing synchronized recovery log points in an infrastructure having at least a first database management system and a second database management system, whereby recovery log files are written and log points are created separately for each database management system. According to this method, log write of all database management systems is suspended, then, the corresponding log points for each database management system forming a global log point are recorded and log writes of all database management systems are resumed. With this method it is inevitable to suspend or to interrupt transactions, which happen to be “in-doubt” at the time of suspending the log writes.
It is a drawback of this method that additional manual intervention is required in order to find out what happened to such “in-doubt”-transactions after the log writes are resumed.